The fast and accurate identification of biological and chemical agents is not only of great interest within the sensor community, but performs a public service by saving lives. The wide dissemination of inexpensive and accurate sensor systems with very low or zero false alarm rates is critical in order to respond to terrorist threats or accidental exposures. False alarms are very costly and could lead to dilatory responses to subsequent real terrorist threats and accidental exposures.
The effectiveness of the first responders depends upon their knowing what hazardous substance has been detected, the concentration of the hazardous substance and the time of the initial exposure. A sensor system which is fast, inexpensive and accurate, and with a low false alarm rate, is critical in both military and civilian applications.
The false alarm rate can be reduced significantly through the use of multiple orthogonal detection methods. Orthogonal methods detect different physical characteristics of a target agent or substance. For example, optical and gravimetric effects are orthogonal. Gravimetric effects result from mass changes on the resonator, while optical techniques look at the interaction of electromagnetic radiation.
For example, U.S. Pat. No. 5,744,902 to Vig describes detectors using a dual-mode sensor using both a gravimetric and a calorimetric analysis of chemical/biological agents.
However, other than gravimetric and calorimetric, none of the prior art detection systems integrates two or more orthogonal measurements (selected from the following methods: gravimetric, calorimetric, thermal gravimetric, voltage gravimetric, and optical detection methods) into one sensor system, thereby substantially improving the identification of hazardous agents and reducing the false alarm rate.